Patent GB-1465795-A (GB)
Title: Method of and apparatus for automatically cutting out work pieces according to a pattern
IPC: B26D5/00
Filed: 1974-05-17
Abstract: 1465795 Pattern followers GRIESHEIM GmbH 17 May 1974 [18 May 1973 29 Sept 1973] 22016/74 Heading G3N In pattern follower control of workpiece cutting, there are provided on the pattern a predetermined interval before, and possibly after, points where direction change is required, deceleration and possibly acceleration marks to initiate deceleration, and acceleration of sensing head 10 and an associated cutting head. The tracing lead, with respect to a reference location, of a scanning head, being decreased or increased in conjunction with deceleration or acceleration initiation. Acceleration may be initiated, either by acceleration marks on the pattern after direction change points, or in response to the passage of a predetermined time interval. As shown a line or edge of the pattern is detected by one or other of differential photoresistor pairs 20, 21; 22, 23 with leads in relation to sensor pivot 18 of V 1 , V 2  respectively. Upon detection of a deceleration mark (71), Fig. 4 (not shown) by photo-resistor 24, relay coil (32), Fig. 2 (not shown) is energized to reduce, by means of contacts 33, the voltage supply to resolver 15 controlling X and Y motors 17, 16, and part of which is rotated by motor 13, also rotating sensor 10. Reduction in the resolver X and Y output voltages causes a corresponding speed reduction to a value determined by the setting of resistor 73. After a time delay determined by the setting of resistor (75), (Fig. 2) of monostable (36) and during which the deceleration has taken place, relay coil (42) is energized to switch over contacts 43a and 43b the tracing lead being reduced from V 1  to V 2 . After a further delay determined by the setting of monostable (27), both relays are de-energized to increase both the speed and the lead, the corner, or region of extreme curvature having been traced. Alternatively, Fig. 3 (not shown), contacts 33 energized only when both of sensors 24, 25 detect a mark, thus enabling intersecting or closely spaced lines to be traced, are comprised in self held relay (53, 60a), the slow speed and consequently the short lead V 2  being held until an acceleration mark (7 1a) ( Fig. 4) on the pattern is sensed, causing, after a delay due to monostable (55), (Fig. 3), the reversion to high speed and long lead. Acceleration marks are longer than deceleration marks, and the latter delay is such that AND (56), controlling the reversion is enabled only by acceleration marks. In tracing, the output of one of the photo-resistor pairs 20, 21; 22, 23, via amplifier 12, controls the motor 13 and the resolver. There may be a set of deceleration marks controlling deceleration in a sequence of steps, corresponding time delays being set to ensure a corresponding acceleration sequence. The deceleration marks may be on the line to be traced, and further marks can control the acceleration and deceleration, by means of a linear function generator (not shown) of velocity. Relays may be replaced by electronic switching. The cutting may be performed by a ripping knife, laser, plasma or oxy-gas torch working on textile, plastics or metallic materials.